Conventional restoring units are used for example in intake devices of internal combustion engines for motor vehicles or in exhaust gas turbochargers of motor vehicles, if an intake opening or a wastegate bypass in the exhaust gas turbocharger is to be optionally opened or closed by means of a rotatable valve. Such a valve device can be actuated by means of a drive unit, for example an electric motor or similar. For the case where the drive unit is not active, it is frequently desirable that the valve of the valve device is moved automatically into a predetermined position, in which the intake device or respectively the bypass valve is, for example, closed. For example, in this way, in the sense of the so-called “fail-safe” principle, it can be prevented that the valve of the valve device assumes an undefined state in the case of a malfunction or a failure of the drive unit.
DE 10 2010 020 579 A1 describes a pneumatic adjustment element with a housing, the internal volume of which is divided by a membrane into a first and second chamber. The membranes are fixed in position radially externally and are fixed in position internally on an axially movable tappet guided in the housing. The tappet is axially displaceable in the case of an unequal pressure between the two chambers. In one of the two chambers, a spring element is arranged in axial direction of the tappet and is supported on both sides. This spring element serves for the restoring of the tappet into a predetermined initial position.